Field
Embodiments relate to mechanically and electrically coupling printed circuit boards (PCBs). Embodiments relate to mechanically and electrically coupling high frequency PCBs.
Related Art
FIG. 1 illustrates a conventional PCB 105. PCB 105 may include a substrate 115 (e.g., microwave substrate) on a rigid metal layer 120. Typically, the PCB 105 includes several functional sections. For example, a PCB may include an integrated Radio Frequency (RF) transceiver. The functional sections may include several componants 110-1 to 110-n to implement the function. Componants 110-1 to 110-n may include, for example, passive components (e.g., resistors and capacitors) and active components (e.g., transistors and amplifiers). The functional sections may include interconnecting transmission lines 125 (e.g., microstrips or striplines).
Further, in a typical assembly housing there are many PCBs each having a different function and operating characteristics (e.g., frequency and power). For example, in addition to a (RF) transceiver there may be a Power Amplifier (PA) section each manufactured on a separate PCB with a different substrate. High frequency connections between the sections on separate PCBs are typically expensive and introduce electrical interference.
Conventionally, these connections include manually installed wires or metal strips that bridge the two PCBs. FIG. 2 illustrates this conventional interconnection system 200. As shown in FIG. 2, the system 200 includes two PCBs 105 each including a substrate 115 on which an interconnecting transmission line 125 is formed. Bridge 215 interconnects the two PCB's 105 by mechanically and electrically connecting the two interconnecting transmission lines 125.
As one skilled in the art will appreciate the conventional interconnection system 200 illustrated in FIG. 2 may be expensive to manufacture. For example, the expense associated with manually soldering the bridge 215 to each of the two interconnecting transmission lines 125. In addition, the interconnection system 200 may not be as reliable as designs require or provide the preferred electrical performances (e.g., high loss at higher frequencies).
Another conventional system utilizes connectors and/or connectors with cable between the PCBs. FIG. 3 illustrates this conventional interconnection system 300. As shown in FIG. 3A, the system 300 includes two PCBs 105 each including a substrate 115. Connector assembly 305 includes a first part (not shown) attached (e.g., soldered) to the substrate 115. Connector assembly 305 includes a second part (not shown) attached (e.g., soldered) to a cable 310. The cable 310 mechanically and electrically interconnects the two PCB's 105.
Alternatively, as shown in FIG. 3B the system 300 includes two PCBs 105 each including a substrate 115. Connector assembly 315 is attached (e.g., soldered) to one of the substrates 115. Connector assembly 320 is attached (e.g., soldered) to the other of the substrates 115. The connectors 315, 320 are mated together to mechanically and electrically interconnects the two PCB's 105.
As one skilled in the art will appreciate the conventional interconnection system 300 illustrated in FIG. 3 may be expensive to manufacture. For example, the expense associated with purchasing and/or manufacturing cable assemblies. In addition, the interconnection system 300 may not be as reliable as designs require or provide the preferred electrical performances (e.g., high loss at higher frequencies).
FIG. 4 illustrates a conventional PCB 400 having a substrate 115 (e.g., microwave substrate) on a rigid metal layer 120. As shown in FIG. 4 the substrate includes two microstrip (or stripline) formations 405, 410. The two microstrip formations 405, 410 are configured as conventional coupled transmission lines. The conventional coupled transmission lines include four ports P1-P4. Characteristics of coupled transmission lines are generally known. For example, a known characteristic is coupling factor which can be determined by equation 1:
                              C                      3            ,            1                          =                              -            10                    ⁢                                          ⁢                      log            ⁡                          (                                                P                  3                                                  P                  1                                            )                                ⁢          dB                                    (        1        )            
where:                C3,1 is the coupling factor from port P1 (input port) to port P3 (coupled port) where port P2 is a transmitted port and port        P4 is isolated (e.g., grounded);        P1 is the input power at port P1 (input port); and        P3 is the output power at port P3 (coupled port).        
As is known (and shown in equation 1), there is power relationship between ports (P1-P2) and (P3-P4). In otherwords, power is coupled across the coupled transmission lines. As is known, the electrical characteristics of the power coupled across the coupled transmission lines (e.g., frequency, voltage) is based on the physical characteristics (e.g., dielectric constant of substrate 115, width of the two microstrip formations 405, 410 and distance between the two microstrip formations 405, 410) as well as the input electrical characteristics at an input port (e.g., P1).